Flooding, famine seen by 2100 as world's temperature rises

WASHINGTON
-- The odds are dead even that the world's average
temperature will increase at least 5 degrees by the
end of the century, enough to trigger flooding, famine
and drought across much of the globe, according to
a study in today's edition of the journal Science.

Figure 1. As the world warms.
(Frank Augstein / Associated Press)

It's the first time scientists have computed the likelihood
that Earth would get warmer by specific degrees. The
study addresses a key criticism about the issue of
global warming, that of scientific uncertainty, which
the Bush administration has cited for its go-slow
response.

The
study was done by Tom Wigley, a senior scientist at
the U.S. National Center for Atmospheric Research
in Boulder, Colo., and Sarah Raper of the University
of East Anglia in England. Their findings were published
as world leaders meet in Germany to work on a controversial
1997 Kyoto treaty to fight global warming.

The
study concluded that there is a 90 percent chance
global warming will increase Earth's temperature from
3 to 9 degrees by 2100. Wigley and Raper consider
a 5-degree increase most likely.

There is a 50-50 chance Earth will get at least 1
degree warmer by 2030.

Scientists are beginning to use these probability
studies, which set the odds for an event, to try to
understand what global warming might mean in the decades
ahead.

A
probability study "gives you a better feel for how
much you have to worry and how much risk there is
in not doing anything," said Peter Stone, a climate
scientist at the Massachusetts Institute of Technology,
who this week released a similar probability study.
When it comes to global warming, Stone said, "There
is a substantial risk that there will be important
big changes."

The 5-degree increase by 2100 crosses a key threshold
for climate scientists. That would make it hot enough
to cause more tropical disease, droughts, floods,
heat waves and severe weather in general - - potentially
killing or displacing hundreds of millions of people,
according to a February report by a United Nations-sponsored
committee of the Intergovernmental Panel on Climate
Change.

Effects for the United States would be milder than
for countries that have tropical or semitropical climates.
A federal study last year found the United States
could produce more food if temperatures were 5 degrees
higher. But there would be more severe droughts and
flooding, plus inundation of beaches, islands and
marshes.

The vast majority of climate scientists agree the
world is warming because carbon dioxide and other
greenhouse gases from the burning of fossil fuels
trap heat in the atmosphere.

The
study by Wigley and Raper entailed more than 110,000
computations of five key variables. They were: how
much carbon dioxide is emitted, how sensitive the
climate is to carbon dioxide, how much heat the oceans
can absorb, uncertainties in the way carbon dioxide
builds up, and the cooling effects of some other pollutants.

Figure 2. Finding in today's edition of
the journal Science detail the likelihood that
the world's average temperature will increase
at least 5 degrees by the end of the century.
The research was published as leaders of 178 nations
meet in Bonn, Germany, to discuss a proposed climate
treaty. (Frank Augstein / Associated Press)

The MIT climate scientists, using slightly different
assumptions, came up with a 50-50 probability that
the temperature will rise by at least 4 degrees.

Another MIT climate scientist, Richard Lindzen, a
critic of global warming science who did not participate
in either study, said probability estimates are skewed
by biases in what goes into the computer analysis.
Other scientists praised the work.